The formula for determining the number of concurrently running tasks per node is:
min (yarn.nodemanager.resource.memory-mb / mapreduce.[map|reduce].memory.mb, yarn.nodemanager.resource.cpu-vcores / mapreduce.[map|reduce].cpu.vcores) . For you scenario : As you told yarn.nodemanager.resource.memory-mb is configured to 16 GB and yarn.nodemanager.resource.cpu-vcores configured to 40. and I am thinking mapreduce.map/reduce.memory.mb, mapreduce.map/reduce.cpu.vcores default values. min (16GB/1GB,40Core/1Core )=16 tasks for Node. Then total should be 16*4=64 (63+1AM).. I am thinking, Two Nodemanger's are unhealthy (OR) you might have configured mapreduce.map/reduce.memory.mb=2GB(or 5 core). As laxman pointed you can post RMUI or you can cross check like above. Hope this helps. Thanks & Regards Brahma Reddy Battula ________________________________ From: Laxman Ch [laxman....@gmail.com] Sent: Friday, November 06, 2015 6:31 PM To: user@hadoop.apache.org Subject: Re: Max Parallel task executors Can you please copy paste the cluster metrics from RM dashboard. Its under http://rmhost:port/cluster/cluster In this page, check under Memory Total vs Memory Used and VCores Total vs VCores Used On 6 November 2015 at 18:21, sandeep das <yarnhad...@gmail.com<mailto:yarnhad...@gmail.com>> wrote: HI Laxman, Thanks for your response. I had already configured a very high value for yarn.nodemanager.resource.cpu-vcores e.g. 40 but still its not increasing more number of parallel tasks to execute but if this value is reduced then it runs less number of parallel tasks. As of now yarn.nodemanager.resource.memory-mb is configured to 16 GB and yarn.nodemanager.resource.cpu-vcores configured to 40. Still its not spawning more tasks than 31. Let me know if more information is required to debug it. I believe there is upper limit after which yarn stops spawning tasks. I may be wrong here. Regards, Sandeep On Fri, Nov 6, 2015 at 6:15 PM, Laxman Ch <laxman....@gmail.com<mailto:laxman....@gmail.com>> wrote: Hi Sandeep, Please configure the following items to the cores and memory per node you wanted to allocate for Yarn containers. Their defaults are 8 cores and 8GB. So that's the reason you were stuck at 31 (4nodes * 8cores - 1 AppMaster) http://hadoop.apache.org/docs/r2.6.0/hadoop-yarn/hadoop-yarn-common/yarn-default.xml yarn.nodemanager.resource.cpu-vcores yarn.nodemanager.resource.memory-mb On 6 November 2015 at 17:59, sandeep das <yarnhad...@gmail.com<mailto:yarnhad...@gmail.com>> wrote: May be to naive to ask but How do I check that? Sometimes there are almost 200 map tasks pending to run but at a time only 31 runs. On Fri, Nov 6, 2015 at 5:57 PM, Chris Mawata <chris.maw...@gmail.com<mailto:chris.maw...@gmail.com>> wrote: Also check that you have more than 31 blocks to process. On Nov 6, 2015 6:54 AM, "sandeep das" <yarnhad...@gmail.com<mailto:yarnhad...@gmail.com>> wrote: Hi Varun, I tried to increase this parameter but it did not increase number of parallel tasks but if It is decreased then YARN reduces number of parallel tasks. I'm bit puzzled why its not increasing more than 31 tasks even after its value is increased. Is there any other configuration as well which controls on how many maximum tasks can execute in parallel? Regards, Sandeep On Tue, Nov 3, 2015 at 7:29 PM, Varun Vasudev <vvasu...@apache.org<mailto:vvasu...@apache.org>> wrote: The number of parallel tasks that are run depends on the amount of memory and vcores on your machines and the amount of memory and vcores required by your mappers and reducers. The amount of memory can be set via yarn.nodemanager.resource.memory-mb(the default is 8G). The amount of vcores can be set via yarn.nodemanager.resource.cpu-vcores(the default is 8 vcores). -Varun From: sandeep das <yarnhad...@gmail.com<mailto:yarnhad...@gmail.com>> Reply-To: <user@hadoop.apache.org<mailto:user@hadoop.apache.org>> Date: Monday, November 2, 2015 at 3:56 PM To: <user@hadoop.apache.org<mailto:user@hadoop.apache.org>> Subject: Max Parallel task executors Hi Team, I've a cloudera cluster of 4 nodes. Whenever i submit a job my only 31 parallel tasks are executed whereas my machines have more CPU available but still YARN/AM does not create more task. Is there any configuration which I can change to start more MAP/REDUCER task in parallel? Each machine in my cluster has 24 CPUs. Regards, Sandeep -- Thanks, Laxman -- Thanks, Laxman